Many types of devices have been developed over the years for the purpose of converting liquids into aerosols or fine particles readily converted into a gas-phase. Many such devices have been developed, for example, to prepare fuel for use in internal combustion engines. To optimize fuel oxidation within an engine's combustion chamber, the fuel must be vaporized, homogenized with oxidizer (e.g. air), and in a chemically-stoichiometric gas-phase mixture. Ideal fuel atomization and vaporization enables more complete combustion and consequent lower engine out pollution. In the case of underwater or high altitude engine operation, the oxidant may more effectively be of another fluid (gas or liquid). In special service applications, the oxidant is selected based upon its efficacy for combustion irrespective of costs. Another factor of oxidant selection is mass per oxidizing unit (e.g., hydrogen peroxide etc.).
More specifically, relative to internal combustion engines, stoichiometricity is a condition where the amount of oxidant required to completely burn a given amount of fuel is supplied in a homogeneous mixture resulting in optimally correct combustion with no residues remaining from incomplete or inefficient oxidation. Ideally, the fuel should be completely vaporized, intermixed with air, and homogenized prior to ignition for proper oxidation. Non-vaporized fuel droplets do not ignite or combust completely in conventional internal and external combustion engines, which degrades fuel efficiency and increases engine out pollution.
Attempts to reduce or control emission byproducts by adjusting temperature and pressure typically affects the NOx byproduct. To meet emission standards, these residues must be dealt with, typically requiring after treatment in a catalytic converter or a scrubber. Such treatment of these residues results in additional fuel costs to operate the catalytic converter or scrubber and may require additional component costs as well as packaging and mass implications. Accordingly, any reduction in engine out residuals resulting from incomplete combustion would be economically and environmentally beneficial.
Aside from the problems discussed above, a fuel that is not completely vaporized in a chemically stoichiometric air/fuel mixture causes the combustion engine to perform at less than peak efficiency. A smaller portion of the fuel's chemical energy is converted to mechanical energy when fuel is not completely combusted. Fuel energy is wasted and unnecessary pollution is created. Thus, by further breaking down and more completely vaporizing the fuel-air mixture, better fuel efficiency may be available.
Many attempts have been made to alleviate the above-described problems with respect to fuel vaporization and incomplete fuel combustion. In automobile engines, for example, inlet port or direct fuel injection have almost universally replaced carburetion for fuel delivery. Fuel injectors spray fuel directly into the inlet port or cylinder of the engine and are controlled electronically. Injectors facilitate more precise metering and control of the amount of fuel delivered to each cylinder independently relative to carburetion. This reduces or eliminates charge transport time facilitating optimal transient operation. Nevertheless, the fuel droplet size of a fuel injector spray is not optimal and there is little time for the fuel to mix with air prior to ignition.
Some types of fuel delivery systems require a source of compressed air to properly delivery fuel to the cylinder for combustion. The compressed air is typically provided by the engine, a compressor component operated by the engine, or electrically off-board of the engine. Challenges exist related in providing a source of compressed air for the fuel delivery system when starting the engine before the compressor is operating.